In constructing driveways, walkways, roadways and the like three types of materials are typically used; namely, asphalt, concrete or paving stones. Interlocking paving stones are generally considered to result in a more aesthetically pleasing visual effect than unfinished asphalt or concrete, but they are relatively expensive to fabricate and install.
Various methods and apparatuses for imprinting surface patterns in cementitious materials, such as concrete, are known in the prior art. For example, U.S. Pat. Nos. 3,832,079 and 3,910,711 which issued to Moorhead on Aug. 27, 1974 and Oct. 7, 1975 respectively, relate to a method and apparatus for imprinting a pattern into uncured concrete. The Moorhead process involves the use of an axle mounted pattern roller having blades which are impressed into the uncured concrete to simulate the appearance of blocks, bricks, cobblestones and the like. A plastic film is positioned between the roller blades and the concrete surface to act as a release agent and to prevent binding or gouging of the concrete.
U.S. Pat. No. 4,105,354, which issued to Bowman on Aug. 8, 1978, teaches a wheel-like forming tool for imprinting surface patterns in a slab of freshly cast, plastic concrete. The concrete-penetrating blades are mounted on the exterior of the wheel frame in a gridlike fashion. A series of pattern forming wheels may be interconnected together to imprint large slabs of concrete, thus overcoming the disadvantages of fixed-width rollers, such as the Moorhead apparatus referred to above.
Such prior art concrete pattern forming methods and apparatuses are not specifically adapted for imprinting hot bitumastic surfaces, such as asphalt. For example, some plastic or rubber-based concrete pattern formers cannot withstand the high temperature of freshly rolled asphalt (typically on the order of 275.degree.-300.degree.). Similarly, some release agents for preventing adherence between the pattern former and the concrete surface are not suitable for use with hot, petroleum-based asphalt. Further, several of the prior art concrete forming tools are substantially rigid and would tend to bend or deform when impacted into the asphalt surface with a high degree of pressure (such as by using a double drum roller).
Accordingly, the need has arisen for a method and apparatus for imprinting freshly rolled asphalt surfaces to simulate the aesthetically pleasing features of cobblestones, interlocking paving stones and the like.